Fire-resistant building board and process



United States Patent Ofifiee Patented Jan. 24, 1967 3,300,372FIRE-RESISTANT BUILDING BOARD AND PROCESS Donald R. Bauer, St. Helens,Oreg., assignor to Kaiser Gypsum Company, Inc., Oakland, Calif., acorporation of Washington N Drawing. Filed Aug. 23, 19 63, Ser. No.304,261

19 Claims. (Cl. 162145) This invention relates to the production of afibrous product such as a building board; and more particularly to theproduction of a fire-resistant board.

In the manufacture of fiber boards for structural, including acousticalor sound-absorbing, purposes a great problem has been the retention ofvarious additives in the fibrous mass upon removal of the slurry waterby drainage, e.g., on a screen; and concomitant problems have been theprovision of such boards of desired strength and density. In one wetmethod of making such boards, a slurry of wood or lignocellulose, ormineral fibers or mixtures thereof in water along with clay, and, ifdesired, other additives, the slurry having low solids content, e.g., 3%thereof, is pumped to a forming device, such as a Wire screen of wellknown type, and water is drained off, leaving a mass of the fibers ingenerally board form. However, in order to avoid loss of additivesthrough the screen, some means of retention must be provided. One knownmeans has been the incorporation of a substance which will coagulate orfiocculate the additive to form agglomerates of such size that they willnot pass through the fibers and screen, and thus are retained. Anothermeans has been to use additive such as formaldehyde resin which-willreact with the fiber, especially wood fiber, to improve retention. Othermeans for improving retention of additives have been known in makingfibrous board products, but the prior art methods have required heatingto fuse addition agents or have required chemical reaction of thevarious addition agents; and this art has desired a simple, inexpensivemethod for dispersing materials in water slurry and for retainingadditives, with production of a strong, resistant board, andparticularly to produce a self-sustaining, strong board, exhibiting highfire-resistance.

According to the present invention there is obtained a strong, fibrousboard of desired density and uniform composition consisting essentiallyof a major amount of mineral fibers, a minor amount of lignocellulosefibers, clay, starch, sizing agent and a cationic surface active agent.A suitable aqueous slurry of these components is prepared, and is thenformed into board on a forming machine, suitably of conventional typewell-known in this art. The formed board or mat is then processed anddried in the known manner. Preferably the board or product consistsessentially of from 60% to 70% mineral fibers, from 1% to lignocellulosefibers, from 10% to clay, from 5% to 15% starch, from 0.5% to 4% sizingagent and from 0.2% to 2.25% of a cationic surface active agent. Theproduct has good strength, exhibits the desired density and isfire-resistant.

The mineral fibers useful herein include any artificially formed orsynthetic inorganic fibrous material such as mineral wool, slag wool,glass Wool, spun glass filaments, or the like and admixtures of suchfibers with each other. In a preferred embodiment there is employedmineral wool, glass wool, or spun glass filaments or admixtures of thesewith each other and, if desired, with a small amount, up to about 5%, ofasbestos fiber added thereto. Chrysotile asbestos has given good resultsin such composition.

The lignocellulose fibers employed herein include wood fibers, bagassefibers or other vegetable fibers, for example, wood fibers derived fromwood chips or the like. The lignocellulose fibers can be very coarsefibers, but preferably are finer or more highly refined fibers such aspaper fibers or the like. It is preferred that such refined fibersexhibit a Canadian 3-gram freeness of greater than 350.

There is employed in the present composition and article any desiredstarch, such as milo starch, corn starch or the like; and very goodresults. have been obtained in one embodiment of present invention usinguncooked tapioca starch. If desired, in one mode of operation, acationic starch is employed, as will be further discussed below. Thestarch can be added in dry state or it can be slurried in water and suchslurry then added to the fibrous slurry or furnish.

The clay which is employed is preferably a non-swelling clay, such askaolin, ball clay or the like. Excellent results are obtained when usingclay of very small ultimate particle size, such as a ball clay whichslurries readily in water. The clay can be pre-milled or it can beincorporated in as-received state in the aqueous fibrous slurry and ithas been found that the clay is broken down, upon mixing into suchslurry, into very fine particles and becomes Well dispersed through themass. One such clay which is found to be very useful herein is known asKlondike clay and another is Tennessee ball clay.

There is also included from 1% to 4% of a sizing agent, which can be anydesired sizing agent known in this art. For instance, there can beemployed an aqueous bituminous or asphalt emulsion such as that known asBitusize or as described in US. Patent 2,481,734, issued September 6,1949, in the names of Watts et al. A very good size is an aqueous waxemulsion or aqueous waxrosin emulsion.

A cationic surface active agent is also incorporated in the compositionand process of this invention. There is employed as such agent, forexample, an aliphatic long carbon chain polyamine, such as that known asDuomac which is made and sold by Armour Industrial Chemical Company,Chicago, Illinois, and which has the formula R-(NH -CH 'CH -CH -NH WhereR is a hydrophobic group having from 8 to 22 carbon atoms and x is aninteger of from 1 to 3, or a water-soluble salt thereof, as described inU.S. Patent 2,862,880 issued December 2, 1958, in the name of Harry J.Clemens. Other cationic surface active agents useful herein include amono-alkyl quarternary ammonium compound, e.g. such a compound as thatknown as Arquad also sold by Armour Industrial Chemical Company,above-mentioned. Alternatively, there can be employed a stronglycationic high molecular weight polymer which is the reaction product ofan alkylene polyamine and a polyfunctional halohydrin, known as Nalco632, made and sold by Nalco Chemical Company, Chicago, Illinois; oranother cationic agent such as lauryl trimethyl ammonium chloride orbromide, cetyl pyridinium bromide or the like. The cationic surfaceactive agent is used in an amount of from 0.2% to 2.25% based on thetotal dry weight of the composition.

In one embodiment of the process of the invention there is prepared adilute furnish or slurry of the lignocellulose fibers in water; andthere is separately prepared a slurry in water of mineral fibers, theclay and a portion, preferably less than 50%, of the cationic surfaceactive agent. The starch is separately made into a slurry in Water. Thelignocellulose furnish is admixed with the mineral fiber-containingslurry and the sizing are added thereto. The remainder, or at least 50%of the total, of cationic agent, preferably in dilute water solution,e.g., containing about 1% concentration of such agent, is then mixedwith the fibrous slurry just prior to feeding to the board-forming Zoneor device, where the slurry is formed into board in the known way withremoval of water. In another embodiment of the present process, thesteps above are also practiced except that, instead of admixing the claywith the mineral fiber slurry, the clay is made into a slurry with thestarch and then mixed into or with the fibrous slurry. Other variationscan also be practiced. However, it is preferred to admix a minorportion,

or less than 50% of the total, of cationic surface active agent, priorto or at the same time as the addition of the clay, and to add at least50% of such agent just prior to feeding to the forming zone. Forinstance, the latter amount can be added in the fan pump normallydisposed just prior to introduction to the Fourdrinier machine or in theslurry flowing from the machine chest, where the starch and size areadded, to the fan pump or the like, or it can be admixed in the trayWater recycled from the forming machine to the slurry flowing to the fanpump.

In practicing the process of the invention, it has been found that atleast a portion, preferably at least 50% of the cationic agent must beadded just prior to introduction of the slurry to the forming machine,that is to say, after all violent or turbulent mixing or treatment hasbeen completed, in order to effect good retention in the formed board ofthe additives, including the clay. It is believed that the cationicagent in part attaches itself to the fibers of the mass and in part tothe particles which it is desired to retain, by electrostatic or ionicbonds or forces, and that these are easily broken or disrupted bymechanical stresses. On the other hand, the addition of the cationicagent effects excellent dispersion of the mineral fibers in the slurryand it is advantageous to add a minor proportion, or less than 50% ofthe total, thereof in the slurry at an earlier stage, or duringpreparation of the primary mineral fiber slurry. The cationic agent isadded as a dilute solution in water in order to obtain good and rapiddispersion in the furnish and maximum effectiveness, and preferably atnot over about 1% by weight concentration in water. It has been foundherein that a cationic surface active agent which acts on the mineralfibers to provide good dispersion, also effects good retention of theclay, and other additives. It is believed that the cationic agent actsas a means of bonding the fibers and additive particles into a compositemass; and it has been found herein that these desired effects areespecially effectively attained when the cationic agent is added in theamounts and manner shown herein. It has also been found that theincorporation of a small amount, up to of asbestos fibers improves thebehavior of the board under fire tests, reducing sag at hightemperatures and having other good effects. The addition of a minoramount of wood fibers also aids in effecting rapid dispersion of themineral fibers, especially mineral wool, in the water of the slurry.

Except as otherwise defined herein, the making up of the variousslurries is carried out according to usual good practice in this art.For instance, the wood fiber-water slurry contains generally from 2% to5%, preferably about 3%, by weight solids; the aqueous slurry of clay,cationic agent and mineral fiber, when admixed in this manner, generallycontains from 2% to 6%, preferably about 3.5% mineral fiber, andpreferably about 4.0% total solids in suspension. The aqueous starchslurry contains about 3.5 lbs. dry starch solids per gallon of water,but this can be varied as desired. The dry size is, if desired, directlyadmixed into the starch slurry. As is known, it is generally preferredthat the final slurry going to the forming zone, e.g. to the Fourdriniermachine, have a total solids content of about 1% to 4% by weight.

However, the process of this invention comprises admixing a small amountof wood fiber slurry with a mineral fiber slurry and incorporation of aminor portion of a total amount of cationic surface active agenttherewith, prior to or simultaneously with admixture of additives suchas clay, starch or size. At least 50% of the total amount of cationicsurface active agent is incorporated with gentle mixing just prior tointroduction to the form ing zone and after all turbulent mixing hasbeen effected.

The 'board produced according to this invention is a self-sustaining,strong product of good fire-resistance and desired density, suitable forwall panels or acoustical board or tile. It can be prepared in anydesired thickness, e.g. of /2" to 1" thickness. The board, after formingin the usual way on a Fourdrinier or other machine, is dried at 200 F.to 600 F., preferably at temperatures of 300 F. to 500 F., and is thenready for use. Preservatives or fungicides can also be incorporated inthe board composition, if desired, in the known manner.

In one mode of carrying out the method of this invention from 60% to 70%synthetic mineral fibers, from 10% to 30% clay and from 0.1% to 0.5%cationic surface active agent are admixed with water to form a primaryslurry containing about 4% solids. From 1% to 10% lignocellulose fibersare separately slurried in water preferably to about 3% fibers in water;and the primary slurry and the lignocellulose slurry are intimatelyadmixed. There is then added thereto from 5% to 15% of starch as a waterslurry, e.g. containing about 4 lbs. starch per gallon of water, andfrom 0.5 to 4% sizing agent to form a furnish containing not over about4%, preferably about 3%, solids; and then there is intimately admixedwith such furnish, just before going to a fan pump, i.e. just prior tointroduction to the Fourdrinier screen, from 0.1% to 1.75% of cationicagent. The total slurry is then fed to the forming machine and formedinto board in the usual way, with removal of most of the water bydrainage, and, if desired, by passage through pressing rolls, followedby heating. The heating temperatures are from 200 F. to 60 F., and,where uncooked starch is incorporated in the furnish, such heatingserves also to cook it in this drying step. The percentages of thevarious components shown above are based on the total dry composition.

In another mode of carrying out the process of this invention, there isprepared an aqueous slurry of wood fibers, e.g. as derived from woodchips by steam digestion followed by refining; and there is separatelyprepared an aqueous slurry of mineral fibers and from 0. 1% to 1.0%cationic agent, all in concentrations and of the type describedelsewhere herein. To the admixture is then added a slurry of starch,size and clay which has been separately prepared by admixing such agentswith water. To this admixture, after thorough mixing, there is added asecond amount of the cationic surface active agent to make a totalamount thereof of from 0.5 to 2.25%, the second amount being at least50% of the total. It will be understood that more than one cationicsurface active agent can be employed to constitute the total amount.

If is an advantage of the present invention that a strong board productof suitable density and acoustical properties is obtained. It is afurther advantage that the additives provided in the furnish areefficiently retained in the fibrous mass upon drainage of water; and afurther advantage is that the board is of substantially uniformconsistency, with excellent interdispersion of the components andfreedom from matting or excessively dense portions. Board of half-inchthickness made according to this invention exhibits tensile strengths ofat least 1500 lbs. per sq. ft.; and not over 5 by volume waterabsorption.

The following example will illustrate one mode of carrying out themethod of this invention.

Approximately 700 lbs. of mineral W001, 150 lbs. of Tennessee ball clay,of minus micron particle size, and 1.4 lbs. of Duomac T as describedabove are admixed with water to form a slurry, called for convenience aprimary slurry. A separate dilute slurry in water is prepared with 30lbs. of wood fibers, or broke pulp. The pnimary slurry and the woodfiber slurry are then thoroughly mixed together, and there are alsoincorporated about 13 lbs. of an asphalt emulsion commercially availableand known as Bitusize, and containing approximately 7.3

lbs. asphalt solids, about 125 lbs. of tapioca starch and about 1.5 lbs.arsenic trioxide as preservative, to give a furnish containing about 3%totalsolids. This furnish enters the fan pump where there is added about3.3 lbs. of Duomac T- (describedabove) as a 1% solution in water and thewhole is fed through the fan pump to the forming machine. In the formingzone, the water drains off, the board passes under a pressing belt andthen through the usual rolls to squeeze out more water and reduce thethickness of the board. The board then goes to-a heated drier, and thefinal dried product exhibits very" good strength and is at least 85%noncombustible. I-texhibits good fire-resistance and acousticalqualities, and low water absorption after being finished, for exampleafter hot calendering, painting and punching, or otherwise finishing, asdesired.

It will be understood that various'modifications and variations can bemade herein without departing from the spirit and scope of the claims.The clay used herein is a non-swelling clay, i.e., one that does notswell when admixed with water. All percentages and parts are by weightunless otherwise indicated. As a cationic active agent there can beemployed a cationic starch, available in commence, such as Cato 8, madeand sold by National Starch and Chemical Company, Plainfield, Michigan;and when used, it is, if desired, pre-oooked in water with a portion ofanother cationic agent as described hereinabove, and the pre-cooked massis admixed with the fibrous slurry just prior to introduction to theforming zone. The non-cationic or dry starch, such as tapioca or otherstarch, dis-closed hereinabove, is added as a binder; and it has beenfound advantageous in one embodiment to add it in uncooked state,whereby it cooks or gelatinizes during the drying step when the formedboard is subjected to the drying temperatures described hereinabove. Theminor amount of lignocellulose fibers is believed to facilitate rapidand complete dispersion of the synthetic mineral fibers to form auniform slurry thereof in water. The addition of a portion of the totalcationic active agent in the mineral fiber slurry also facilitatesdispersion of fibers therein and, additionally, it acts to bond allfibers, clay and starch together. It is believed that this bondingaction is not strong and it tends to break down upon vigorous agitation;and, therefore, a further amount of cationic surface active agent isadded, With gentle agitation, just prior to forming to effect adequatebonding and to enable retention in the fibrous mass or board of thestarch, clay and other additives incorporated in the slurry feed. Theterm furnish as used herein designates a slurry in water of theingredients mentioned.

Having now described the invention, what is claimed is:

1. A self-sustaining, fibrous board consisting essentially of a majorportion of synthetic mineral fibers, a minor portion of lignocellulosefibers, from 5% to 15% starch, from to 30% clay, 0.5% to 4.0% sizingagent, and from 0.2% to 2.25 of cationic surface active agent.

2. A board as in claim 1 wherein said lignocellulose fibers are refinedfibers having a Canadian 3-gram freeness of at least 350.

3. A self-sustaining, fibrous board consisting essentially of a majoramount of synthetic mineral fibers, a minor amount of lignocellulosefibers, from 5% to starch, from 10% to 30% clay, 0.5% to 4.0% sizingagent, a small amount, up to 5% asbestos fibers, and from 0.2% to 2.25cationic surface active agent.

4. A self-sustaining, fire-resistant board consisting essentially offrom 60% to 70% synthetic mineral fibers, from 1% to 10% lignocellulosefibers, from 5% to 15% starch, from 10% to 30% clay, from 0.5% to 1.0%sizing agent, and from 0.2% to 2.25% of a cationic surface active agent.

5. A board as in claim 4 wherein said synthetic mineral fiber is mineralwool.

6. A board as in claim 4 wherein said clay is ball clay.

7. A board as in claim 4 wherein said lignocellulose 6 fibers arerefined fibers having a Canadian 3-gram freeness of at least 350.

8. A board-as in claim 4 wherein said cationic surface active agent isselected from the group consisting of a long carbon chain aliphaticpolyamine and water soluble salts thereof.

9. A self-sustaining, fibrous board consisting essentially of from 60%to 70% synthetic mineral fibers, from 5% to 15% starch, from 1% to 10%lignocellulose fibers, from 10%to 30% clay, from 0.5% to 4.0% sizingagent, a small amount, up to 5%, asbestos fibers, and from 0.2% to 2.25%cationic surface active agent.

10. A board as in claim 9 wherein said lignocellulose fibers are refinedfibers having a Canadian 3-gram freeness of at least 350.

11. An aqueous slurry suitable for forming a self-sust-aining, fibrousboard consisting essentially of from 60% to 70% synthetic mineralfibers, from 1% to 10% lignocellulose fibers, from 5% to 15% starch,from 10% to 30% clay, from 0.5% to 4.0% sizing agent, and from 0.2% to2.25% cationic surface active agent, all said amounts being percent byweight on the dry basis, and sufficient water to make a dilute slurry.

12. Slurry as in claim 11 wherein said mineral fibers are mineral wool.

13. Slurry as in claim 11 wherein said l'gnocellulose fibers are refinedfibers having a Canadian 3-gram freeness of at least 350.

14. A fire-resistant fibrous board consisting essentially of from 60% to70% mineral fibers, from 1% to 10% lignocellulose fibers, from 10% to30% clay, from 5% to 15% starch, from 0.5% to 4% sizing agent and from0.2% to 2.25% of a cationic surface active agent.

15. Process for producing a fibrous board comprisng (a) preparing aslurry of lignocellulose fibers in water, (b) separately preparing aslurry of synthetic mineral fibers and a cationic surface active agentin water, (c) admixing said two slurries together, (d) admix ng withsaid admixture a suspension of clay and starch in water, (e) adding tosaid last-mentioned admixture a sizing agent, (f) then admixingtherewith with gentle agitation a further amount of a cationic surfaceactive agent, (g) introducing the resulting mixture to board-formingzone and (h) forming into board with removal of water, saidlignocellulose fibers being present in minor amount andsaid mineralfibers being present in major amount, based on the total dry weight ofthe mass.

16. Process for producing a fibrous board comprising (a) preparing aslurry of lignocellulose fibers in water, (b) separately preparing aslurry of synthetic mineral fibers, clay and a cationic surface agent inWater, (c) admixing said two slurries together, (d) admixing starch anda sizing agent with said admixed slurries, (e) then admixing therewithwith gentle agitation a further amount of a cationic surface activeagent, (f) introducing the resulting admixture to a board-forming zoneand (g) forming into board with removal of water, said lignocellulosefibers being present in minor amount and said mineral fibers beingpresent in major amount, based on the total dry weight of the mass.

17. In a process for producing a fibrous board wherein there is prepareda water slurry of a major portion of synthetic mineral fibers, a minorportion of lignocellulose fibers, starch, clay and a sizing agent, andsaid slurry is formed into board with removal of water, the improvementwhich comprises separately preparing a slurry of said lignocellulosefibers in water, separately preparing a water slurry of said syntheticmineral fibers and a cationic surface agent, admixing said two slurriestogether, adding with gentle agitation a further amount of cationicsurface active agent to the total slurry just prior to introduction tothe forming zone, then introducing the resulting admixture to aboard-forming zone and forming said slurry into board with removal ofwater.

18. Process as in claim 17 wherein less than one-half of the totalamount of said cationic surface active agent is added in saidfirst-mentioned mineral fiber water slurry, and the remainder of saidtotal agent is added just prior to said introduction to said formingzone.

19. In a process for producing a fibrous board wherein there is prepareda water furnish containing a major portion of synthetic mineral fibers,a minor portion of lignocellulose fibers, starch, clay and a sizingagent, and said furnish is formed into board with removal of water, theimprovement which comprises preparing a water slurry containing saidlignocellulose fibers in an amount to provide from 1% to 10% thereof inthe total dry mass, separately preparing a water slurry containing saidsynthetic mineral fibers in an amount to provide from 60% to 70% thereofin the total dry mass, and from 0.1% to 0.5%, based on total dry massweight, of a cationic surface active agent, admixing said two slur'riestogether,

then incorporating therein said starch, clay and sizing agent, thenadding With gentle agitation a further amount of said cationic surfaceactive agent to provide a total thereof of from 0.2% to 2.25%, based ontotal dry mass weight, and thereafter introducing said admixture to aboard-forming zone.

References Cited by the Examiner DONALL H. SYLVESTER, Primary Examiner.H. CAINE, Assistant Examiner.

1. A SELF-SUSTAINING, FIBROUS BOARD CONSISTING ESSENTIALLY OF A MAJORPORTION OF SYNTHETIC MINERAL FIBERS, A MINOR PORTION OF LIGNOCELLULOSEFIBERS, FRM 5% TO 15% STARCH, FROM 10% TO 30% CLAY, 0.5% TO 4.0% SIZINGAGENT, AND FROM 0.2% TO 2.25% OF CATIONIC SURFACE ACTIVE AGENT. 15.PROCESS FOR PRODUCING A FIBROUS BOARD COMPRISING (A) PREPARING A SLURRYOF LIGNOCELLULOSE FIBERS IN WATER, (B) SEPARATELY PREPARING A SLURRY OFSYNTHETIC MINERAL FIBERS AND A CATIONIC SURFACE ACTIVE AGENT IN WATER,(C) ADMIXING SAID TWO SLURRIES TOGETHER, (D) ADMIXING WITH SAIDADMIXTURE A SUSPENSION OF CLAY AND STARCH IN WATER, (E) ADDING TO SAIDLAST-MENTIONED ADMIXTURE A SIZING AGENT, (F) THEN ADMIXING THEREWITHWITH GENTLE AGITATION A FURTHER AMOUNT OF A CATIONIC SURFACE ACTIVEAGENT, (G) INTRODUCING THE RESULTING MIXTURE TO BOARD-FORMING ZONE AND(H) FORMING INTO BOARD WITH REMOVAL OF WATER, SAID LIGNOCELLULOSE FIBERSBEING PRESENT IN MINOR AMOUNT AND SAID MINERAL FIBERS BEING PRESENT INMAJOR AMOUNT, BASED ON THE TOTAL DRY WEIGHT OF THE MASS.